This may not be totally right but I think the theory is that increased use of energy has increased the CO2 in the atmosphere which may result in temperature increases which may cause the climate to change.

I was watching a science video today (which I can't link to as it's behind a pay wall) on water. One of the comments was that "more energy is used in the water cycle every 24 hours around the planet earth than man has been able to generate in the course of history".

Interesting I thought.